Diatom Assemblage Shifts Driven by Hydrological Regulation and Nutrient Dynamics in Lake Baiyangdian, the Largest Freshwater Wetland on the North China Plain

Abstract

Lake Baiyangdian, the largest natural freshwater wetland on the North China Plain, has faced multiple stressors from anthropogenic disturbances and climate change, affecting its aquatic ecosystem over the past century; however, little is known about the presence and timing of abrupt changes in aquatic communities. In this paper, we reconstructed ecological changes in Lake Baiyangdian over the past 70 years based on diatom assemblages and identified ecological shifts by the Sequential t test Analysis of Regime-shifts algorithm (STARS) and a sequential F test. Our results revealed that the first ecological shift in the diatom community in ~1963 was associated with damming in the basin. This hydrological modification prolongs hydraulic residence time and thus accelerates nutrient retention, leading to the development of eutrophic species such as C. meneghiniana. The second ecological shift occurred in the 1990s and was characterized by the onset of eutrophication with reduced water clarity and increased eutrophic species abundance. This shift was mainly attributed to enhanced nutrient enrichment from human activity intensification, as well as an increase in the regional temperature. Our study details the complex trajectories of the aquatic ecosystem shifts driven by increasing hydrological alteration, nutrient loading, and climate change in Lake Baiyangdian and offers recommendations for improved management.

Keywords: Ecological shift, Diatoms, Hydrological alteration, Human activity, Climate change, Lake Baiyangdian